Foods High in Both Fructans and GOS: A Comprehensive Guide

Navigating dietary restrictions can be challenging, especially when dealing with multiple food sensitivities. For those following a low FODMAP diet or managing irritable bowel syndrome (IBS), understanding which foods contain both fructans and galacto-oligosaccharides (GOS) is crucial. These two carbohydrate groups are common triggers for digestive discomfort, and unfortunately, several foods contain significant amounts of both.

This comprehensive guide will help you identify foods high in both fructans and GOS, understand why they can cause digestive issues, and discover suitable alternatives to maintain a balanced diet while avoiding these potential triggers.

Understanding Fructans and GOS

Before diving into specific foods, it's important to understand what fructans and GOS actually are. Both belong to the FODMAP family (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols), which are short-chain carbohydrates that can be poorly absorbed in the small intestine.

Fructans are chains of fructose molecules that end with a glucose molecule. They're found in various foods including wheat, onions, and garlic. The human digestive system lacks the enzymes needed to break down fructans in the small intestine, so they travel to the large intestine where gut bacteria ferment them, potentially causing gas, bloating, and other IBS symptoms in sensitive individuals.

GOS (galacto-oligosaccharides) are chains of galactose sugars with a glucose molecule at the end. Like fructans, humans lack the enzymes to digest GOS properly, leading to fermentation in the large intestine. Common sources include legumes, certain nuts, and some vegetables.

Why These Carbohydrates Cause Digestive Issues

When fructans and GOS reach the large intestine undigested, gut bacteria feast on them through fermentation. This process produces gases like hydrogen, methane, and carbon dioxide. For people with IBS or FODMAP sensitivities, this excessive gas production can lead to uncomfortable bloating, abdominal pain, and altered bowel habits.

The osmotic effect of these carbohydrates also draws water into the intestine, which can cause diarrhea in some individuals. The combination of both fructans and GOS in a single food can amplify these effects, making such foods particularly problematic for sensitive individuals.

Legumes: Double FODMAP Offenders

Legumes are perhaps the most notorious food group containing both fructans and GOS in significant amounts. This family includes beans, lentils, chickpeas, and peas, which form the protein backbone of many vegetarian and vegan diets.

Beans and Their FODMAP Content

Kidney beans, black beans, navy beans, and pinto beans all contain substantial amounts of both fructans and GOS. A typical serving of kidney beans (around 1/2 cup cooked) can contain up to 2.24g of GOS and 0.31g of fructans. This combination makes beans particularly challenging for those with FODMAP sensitivities.

The notorious reputation of beans for causing gas is directly related to their high content of these fermentable carbohydrates. While beans offer excellent nutritional benefits—including protein, fiber, iron, and other minerals—their FODMAP content makes them problematic for many with digestive sensitivities.

Chickpeas and Lentils

Chickpeas (garbanzo beans) and various lentil varieties also contain significant amounts of both fructans and GOS. Chickpeas, the main ingredient in hummus and a staple in Mediterranean and Middle Eastern cuisines, contain approximately 1.2g of GOS and 0.2g of fructans per 1/2 cup serving.

Lentils, while slightly lower in FODMAPs than some other legumes, still contain enough of both fructans and GOS to trigger symptoms in sensitive individuals. Red, green, and brown lentil varieties all contain these fermentable carbohydrates, though in varying amounts.

Reducing FODMAP Content in Legumes

If you're not ready to eliminate legumes entirely, certain preparation methods can help reduce their FODMAP content. Soaking dried beans for 24 hours (changing the water several times) and discarding the soaking water before cooking can help leach out some of the water-soluble FODMAPs. Sprouting legumes before cooking can also reduce their FODMAP content as the germination process uses some of these carbohydrates for energy.

Certain Vegetables: Hidden Sources of Both FODMAPs

Several vegetables contain both fructans and GOS, making them potential triggers for sensitive individuals. Understanding which vegetables contain both can help you make informed dietary choices.

Allium Vegetables

The allium family, including onions, garlic, leeks, and shallots, is particularly high in fructans but also contains some GOS. Onions are among the highest fructan-containing foods, with a single tablespoon of onion containing enough fructans to trigger symptoms in sensitive individuals. While their GOS content is lower, the combination can be particularly problematic.

Garlic, another allium vegetable, is extremely high in fructans and contains small amounts of GOS. Even small amounts of garlic (less than a clove) can trigger symptoms in sensitive people. Unfortunately, both onions and garlic are used extensively in many cuisines as flavor bases, making them difficult to avoid in prepared foods and restaurant meals.

Cruciferous Vegetables

Some cruciferous vegetables contain both fructans and GOS, though generally in lower amounts than legumes or alliums. Brussels sprouts, cauliflower, and certain varieties of cabbage contain moderate amounts of both FODMAP types. For example, Brussels sprouts contain approximately 0.32g of fructans and 0.11g of GOS per 1/2 cup serving.

While these vegetables offer significant nutritional benefits—including cancer-fighting compounds, fiber, and vitamins—their FODMAP content means that portion control is important for sensitive individuals. Smaller portions may be tolerated, while larger servings might trigger symptoms.

Grains and Cereals with Dual FODMAPs

Several grains and grain products contain both fructans and GOS, though fructans are typically the predominant FODMAP in this food group.

Wheat and Wheat Products

Wheat is primarily known for its fructan content, but it also contains small amounts of GOS. Products made with wheat flour—including bread, pasta, crackers, and baked goods—can therefore contain both types of FODMAPs. The fructan content increases with the protein content of the wheat, so high-protein wheat products (like certain breads) may be more problematic than others.

The processing of wheat can also affect its FODMAP content. For example, sourdough fermentation partially breaks down fructans, making properly fermented sourdough bread potentially more tolerable for some individuals with mild sensitivities.

Rye and Barley

Rye contains even higher levels of fructans than wheat, along with some GOS. Rye bread, crackers, and cereals can be significant sources of both FODMAPs. Barley, used in many cereals, soups, and beer, also contains both fructans and GOS, though like wheat, the fructan content is higher.

These grains form the basis of many traditional diets, particularly in European cuisines, making them difficult to avoid completely. Fortunately, there are several grain alternatives that are lower in FODMAPs, including rice, corn, quinoa, and oats (in moderate amounts).

Nuts and Seeds: Unexpected Dual Sources

While not all nuts and seeds contain significant amounts of both fructans and GOS, a few varieties do contain both types of FODMAPs in amounts that could trigger symptoms in sensitive individuals.

Pistachios and Cashews

Pistachios are particularly high in both fructans and GOS. A standard serving of pistachios (about 1/4 cup or 30g) contains approximately 0.66g of GOS and 0.32g of fructans. This dual FODMAP content makes pistachios one of the most problematic nuts for those with sensitivities.

Cashews also contain both types of FODMAPs, though in somewhat lower amounts than pistachios. The combination still makes them potentially problematic, especially in larger portions or when consumed alongside other high-FODMAP foods.

Practical Tips for Managing a Diet Low in Fructans and GOS

Navigating a diet that restricts foods high in both fructans and GOS requires planning and knowledge, but it doesn't have to mean a bland or nutritionally inadequate diet.

Finding Suitable Alternatives

For legumes, consider tolerable protein alternatives such as tofu, tempeh, eggs, meat, fish, or poultry. If you're vegetarian or vegan, small portions of well-prepared legumes might be tolerated, or you can explore legumes with lower FODMAP content like canned lentils (rinsed well) or small portions of canned chickpeas.

For allium vegetables, garlic-infused oil and onion-infused oil provide the flavors without the FODMAPs, as the fructans and GOS are not oil-soluble. Chives, the green parts of spring onions, and asafoetida powder (in small amounts) can also provide onion-like flavors without the digestive distress.

Reading Labels and Eating Out

When shopping, be vigilant about reading ingredient labels. Onion and garlic powder, wheat flour, and legume ingredients like chickpea flour are common in processed foods. Terms like "natural flavors" can sometimes hide onion or garlic derivatives.

When dining out, communicate clearly with servers about your dietary needs. Many restaurants are becoming more accommodating of dietary restrictions. Simple dishes with fewer ingredients are generally safer choices, and don't hesitate to ask about ingredients or preparation methods.

Balancing Nutritional Needs

Restricting foods high in both fructans and GOS shouldn't mean compromising nutritional intake. Focus on including plenty of low-FODMAP vegetables, tolerated proteins, and low-FODMAP grains like rice, quinoa, and oats. If necessary, consider working with a registered dietitian who specializes in digestive health to ensure your diet remains nutritionally balanced.

Remember that FODMAP tolerance is highly individual, and many people can reintroduce certain high-FODMAP foods in small amounts after an initial elimination phase. Keeping a food and symptom journal can help identify your personal tolerance levels for different foods containing fructans and GOS.

Conclusion

Understanding which foods contain both fructans and GOS is an important step in managing digestive symptoms for those with IBS or FODMAP sensitivities. While the list of foods containing both can seem daunting—including many legumes, certain vegetables, some grains, and select nuts—there are plenty of alternatives and strategies to maintain a varied, nutritious, and enjoyable diet.

Remember that FODMAP sensitivities exist on a spectrum, and most people don't need to eliminate these foods completely forever. Working with healthcare professionals to determine your individual triggers and tolerance levels can help you develop a personalized approach to managing your diet and digestive health.